Combining electrophysiology and fMRI

Electrophysiological and hemodynamic measures are the two most prominent tools to study brain function non-invasively in humans. The two methodological approaches are thought to provide largely complementary information on how the brain functions. EEG and MEG recordings provide a direct measure of neuronal responses with millisecond resolution, but have a relatively poor spatial resolution and primarily reflect synchronized post-synaptic potentials in the apical dendrites of pyramidal neurons. FMRI on the other hand can inform us about where in the brain changes in neuronal activity occur with millimeter-level precision, while covering the entire brain or a large part of the brain. Hemodynamics-based techniques like fMRI however only provide an indirect measure of neuronal activity with a temporal resolution on the order of seconds. For these techniques to be truly complimentary it is important to understand how they relate to each other. In this presentation I will give an overview of empirical studies by myself and by others in both humans and animals that have investigated the link between electrophysiological data and the BOLD signal. The main focus will be on the link between BOLD/fMRI and neural oscillations measured invasively by the local field potential recordings and non-invasively by MEG and EEG. Neural oscillations in different frequency bands have been directly linked to distinct neural processes, and in particular to different roles in neural communication between brain regions. Relating fMRI results to effects in specific frequency bands in MEG/EEG can therefore substantially help our understanding of the results obtained with fMRI. Conversely, knowing the exact spatial locations or brain regions where neural activity relates to frequency specific changes observed in MEG/EEG can help us understand the role these oscillations have in a specific task context. In this lecture I will provide an overview of work that has investigated how neural oscillations in different frequency bands relate to the BOLD signal. This will include fundamental work in animals, but also own work with simultaneously recorded EEG and fMRI that relates neural oscillations to laminar specific changes in the BOLD signal and to changes in fMRI-based connectivity.

Acknowledgements

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References

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